Solar operated electric switch



J. M. BRADY SOLAR OPERATED ELECTRIC SWITCH Filed Nov. 27, 1945 FIG. I

IN VEN TOR. JAMES M. BRADY Nov. 5, 1946.

HHH

Patented Nov. 5, 1946 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 13 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

My invention relates to solar operated time signal devices and more particularly to solar operated time signal devices for setting the hands of clocks.

In order, over a period of time, to maintainthe accuracy of clocks operated by spring mechanisms, it is necessary, because of the mechanical limitations of such instruments to realign periodically the hands of the clocks in accordance with the setting of a standard clock or the time signals derived from a, standard clock. Unless such resetting is performed a deviation will appear in the clock setting which in time becomes progressively greater.

In clocks actuated by synchronous electric motors, the accuracy of the clock is contingent upon the electric power source. Deviations in the settings will result because of intermittent current interruptions in the power line and the clock must be reset to restore the proper time indication.

The need for individual and manual resetting of clocks has been obviated by the use of electrically operated resetting mechanism, as exemplied in clocks of the Western Union type, which are periodically reset by electric current pulses conveyed over wires to reset mechanisms incorporated in the clock structure. The timing of these current pulses is governed by a standard clock situated at a central station and by the use of a Wire network a plurality of such clocks may be synchronously regulated.

Clocks may be so situated, however, that it is difficult or impractical to feed over wires the current pulses needed to operate the resetting mechanism of the clock.

For example, in "programming clocks employed in conjunction with automatic weather `stations for the purpose of timing and electrically switching the radio transmission of meteorological data, it is of importance to maintain the accuracy of these clocks. Otherwise, in preparing to receive the transmitted data at a point remote from the station, at what is believed to be program time, it may be found that the transmission is already in progress or that it has either transpired or been delayed.` Where it is intended to receive the data of a group of weather stations in a predetermined time sequence, the lack of synchronism among the programming clocks of the various stations is disruptive to intelligible reception.

Inasmuch as automatic weather stations are unattended for prolonged periods, it is desirable to have a system installed for the resetting of the clocks, but because the stations may be isolated and a considerable distance from the central receiving station, a wire network system carrying pulses from a standard clock, of the type previously described, is not feasible.

It is, therefore, an object of my invention to provide a solar operated time signal device for sending an electric current to the reset mechanism oi a clock, which may be disposed in the immediate vicinity of the clock.

Another object of my invention is to provide a solar operated time signal device which is responsive only to the heat rays of the sun and is not affected by ambient temperature.

A further object of my invention is to provide a solar operated timing device which is simple in construction and operation.

It is known that by the use of sun dial, the -time of day may be determined by observing the shadow thrown by a style onto a calibrated dial as the sun traverses its daily transit. If, however, a heat senstive device is so oriented and shielded, that it is responsive to the heat of the suns rays only at a particular instant during the course of the day, this device if made to close an electrical circuit, may be applied to actuate the electrical reset mechanism of a clock.

Accordingly, I have provided a cylinder having a lens disposed at one end thereof which gathers and focuses the suns rays to a point on the other end of the tube. A bimetallic switch is located at the focal point of the lens, which comprises two bimetallic elements having cooperating electrical contacts connected thereon. The elements are exposed to the rays of the sun and are arranged to operate in a differential manner so that only when the rays impinge on one of the elements will the -contacts meet. Thus, the switch will not respond to ambient temperature variations since such variations affect both elements equally. The

tube is held on an adjustable mount permitting orientation in any chosen position in respect to the transit of the sun, hence causing the switch to close at any specific, predetermined interval of time. The closed switch connects an electrical power source to the reset mechanism of the clock, thereby resetting it.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention,

however, both as to its organization and its methe ods of operationy together with additional objects and advantages thereof will be understood from the following description of a specific embodiment when read in connection with the accompanying drawing in which:

Figure 1 is a longitudinal section showing an embodiment of my invention.

Figure 2 is a plan view one of the baiiies dis posed in the cylinder shown in Figure l.

Figure 3 illustrates one of the other elements of Figure 1 namely the bimetallic switch, Figure 3A being a plan view and Figure 3B being an end view.

Referring to the drawing and more particularly to Figure 1, a hollow cylinder IIJ, made of brass or similar material, has its interior surface blackened and one end threaded to receive a metal sleeve II which is similarly threadedalong its inner surface. A convex lens I2 is secured to one end of sleeve II and by rotating sleeve I I, the point of focus of lens I2 may be readily adjusted.

Disposed along the longitudinal axis of the cylinder are a plurality of disc shaped bales I3, I4, I5, and I6 the planes of which are normal to the longitudinal axis. The baiiies are provided with elongated orifices the size of which becomes progressively smaller so that the baffle I6 at the end of the cylinder opposite to that carrying the lens I2 has an orice in the form of a narrow slit.

Fixedly secured to the baliie Iii is a binietallic switch II (to be described in detail in connection with Figure 3), inclosed in a metal housing 3. The switch is connected in series with battery I8 which provides the operating voltage for the resetting mechanism (not shown) housed in clock I9. The cylinder I is positioned in respect to the sun by any suitable means, as for example, a mounted ball and socket swivel (not shown) attached to the cylinder, thereby permitting any desired orientation.

In operation, the rays of the sun 2D strike the convex lens I2 at a time of day determined by the orientation of vthe tube and are converged and brought to a focus at the bimetallic switch 'Il disposed at the opposite end of the cylinder I0. The baiiies function to restrict the solar rays to a `conical path thereby preventing the possibility of reiiection from the interior surface of the tube. The switch is operated by the suns heat and the battery voltage is applied to the reset mechanism in the clocl; which adjusts the hands of the clock to a position in accordance with the time signal device.

Figure 2 shows a plan view of one of the baffles which is provided with an elongated oriiice. The dimensions of the orice are such as toallow for the vertical variation over a period of time in the inclination of the suns rays but to restrict their lateral movement in the tube.

Figure 3 shows the details of the bimetallic switch, 3A being a plan View and 3B being an end view. The corresponding parts in both Yfigures 3A and 3B are numbered identically.

The elements 2l and 22 are identical each being composed of a sandwich of two thin strips of `metals having disparate thermal coeiiicients. The elements are mounted on aninsulating strip 23, which in turn is mounted upon a base 211, thus elevating vthe bimetallic elements 2I and 22 from the base 24 and permitting vertical 4movement toward oraway from the base 24.

The elements 2| and 22 are pivoted by screws 25 and 26 respectively. Lugs 21 and 28 are secured 4 to the ends of the elements 2| and 22 and serve as the terminals or" the switch. At the ends of the bimetallio elements 2| and 22 opposite to that containing the terminals are mounted the switching contacts 29 and 39, contact 29 being directly attached to element 22 while contact 30 is attached to a spring arm 3I which is 'secured to bushing 32 mounted on element 2I.

Adjusting screw 34 is provided for the purpose of varying the initial spacing between the contacts 28 and 29 thereby permitting adjustment of the switch to any desired sensitivity.

When the bimetallic switch is not acted upon by the suns rays, ambient temperature changes will cause the elements 2l and 22 to flex to a degree and in a direction relative to the temperature. However, since both elements are identical and flex to the same degree and in the same direction. the spacing between the contact points 23 and 29 will remain undisturbed and at a distance initially set by adjusting screw 34.

The insulation strip 23 is pro-vided with a slot 33 (shown in dotted lines) which allows the solar radiation to penetrate and fall upon elements 2l and 22, The length of the slot 33 is such as to allow for variations in the suns inclination day by day. The switch is mounted on the tube so that the 'slot 33 coincides in position with the orifice in baille I6.

In operation the radiation in the form of a spot falls rst upon element 2 Ii, which heats and bends bringing contact 28 to bear `upon contact 29, thereby closing the switch and operating the reset mechanism as described in connection with Figure 1. When the spot, which moves with the apparent motion of the sun, falls upc-n element 22, the element will bend in the same direction es element 2I had moved previously thereby drawing contact 29 away from contact 2S and opening the switch.

It is desirable to make the period during which the switch is closed as brief as possible. rIhis may be attained by placing the elements 2l and 22 in close proximity. Since the angle subtended by the disc of the sun at a point on the earths surface is one half of a degree `and the earth makes rone complete revolution in 24 hours, the sun will cross the 1/ degree angle in two minutes. By disposing "the elements 2l` and 22 a sixteenth of an inch apart the timing interval becomes less than one minute duration.

The local current to set the clock will be controlled by the time signal device once per 24 hours unless several such devices are employed. Since the deviation of a well constructed clock during a daily period is not appreciable, such a device even if made occasionally inoperative by clouds obscuring the sun, is sufficient to meet most clock requirements.

Although I have shown and described a specific embodiment of my invention, I do not desire to be limited thereto, as various other modifications of the same may be made 4without departing from the spirit and scope of theiappended claims,

I claim:

1. Asolar operated time signal device comprising in combination, a light converging lens means, a heat responsive electrical switch dispo-sed substantially at the focal point of said lens means, a source of `electrical energy controlled by said switch, said lens and said switch being adapted to be positioned in a plane intersecting the'transit of the sun at any desired point thereon, and means for light shielding said switch whereby it is responsive at the instant the sun is positioned at said point.

-l A.2. A solar operated time signal device compris- 'ing in. combination an elongated housing, said A'housing being disposed in a plane intersecting the transit of the sun at any desired point thereon, a ray concentrating lens means disposed at one end of 'said housing, a heat responsive electrical switch disposed within said housing substantially at the focal point of said lens means whereby said yswitch is responsive at the moment the sun reaches said point in its transit.

3. A solar operated time signal device comprising in combination a substantially cylindrical housing, said housing being adapted to be' posi- 4tioned in a plane intersecting the transit of the `sun to any desired point thereon,.a ray converging lens means disposed at one end of said houspoint in its transit.

4. The combination in apparatus for deriving electrical time signals from solar energy cornprising a heat responsive electrical switch and shielding means arranged to expose said switch at a single point in the transit of the sun whereby said switch operates when the sun occupies said point.

5. A solar-operated time signal device comprising in combination, a cylinder adapted to be positioned in a plane intersecting the transit of the sun at any desired point thereof, a light converging lens disposed at one end of said cylinder, a heat responsive electrical switch disposed within said cylinder at the focal point of said lens, a plurality of baies coaxially disposed in spaced relationship within said cylinder, said baffles having centrally located elongated orices of progressively smaller size, the baille having the largest orifice being disposed adjacent Vto said lens and the baie having the smallest orifice being disposed adjacent to said switch, and a source of electrical energy controlled by said switch.

6. The combination in a heat responsive electrical switch insensitive to ambient temperature comprising a pair of identical bimetallic elements arranged to fiex in the same direction in response to heat, a first electrical contact aiiixed to one of said elements, a second electrical contact aixed to said other element superposed in spaced relationship with said first contact, means for successively directing heat to one of said elements whereby said contacts connect and then to the other of said elements whereby said contacts separate.

'7. A solar operated time signal device comprising in combination an elongated tubular housing adapted to be positioned in a plane intersecting the transit of the sun at any desiredl point thereof; light converging lens means dis.- posed atone end of said housing; a heat responsive electrical switch disposed within said housing substantially at the focal point of said lens means; a plurality of baflles coaxially disposed in spaced relationship within said housing, said baffles having centrally located elongated orices of progressively smaller size, the baffle having the largest orifice being disposed adjacent said lens means and the ballie having the smallest orifice being disposed adjacent said switch; and a source of electrical energy controlled by said switch;

whereby said switch may be actuated when the sun reaches a desired pointof its transit.

. 8,. In anelectrical switching means responsive toa moving light source, the combination including two substantially identical bimetallic heat responsive elements provided with electrical contacts spaced from each other when both of the elements aforesaid are subjected to like temperature, the said contacts being caused to engage each other when the temperature of one of said elements is raised and to again separate when the temperature of the second of said elements is raised; means to direct heat from said moving light source only upon the first of said contacts when the said source is in a predetermined position relative to the said switching means and to direct light only upon the second of said' elements when the said source is in a second predetermined position. 1

9. A heat responsive electrical switch comprising a base; a pair o-f heat responsive bimetallic elements, disposed substantially parallel to each .other and each secured at one end to the said base; a contact secured to the free end of each of said elements, the free ends of said elements being adapted to move simultaneously in one direction with increases in ambient temperature and simultaneously in the other direction with decreases in ambient temperature, so that under like temperatures the contacts are at all times spaced from each other a substantially equal amount; said contacts moving toward each other and into engagement upon raising the temperature of one of said elements higher than that of the other, and said contacts moving away from each other and out of engagement when the second element is subjected to a temperature higher than the first element; and means to subject said elements alternately to a higher temperature; so that irrespective of changes in ambient temperatures the two. contacts will remain out of engagement, but upon subjecting only one element to a higher temperature electrical engagement between the contacts will take place and upon subjecting only the other element to a, higher temperature the said contacts will move out of electrical engagement.

l0. A solar operated electrical switching device comprising an elongated tube; provided with a light converging lens means; a heat responsive switch, positioned substantially at the focal point of said lens means, said switch being provided with an elongated bimetallic electrical engaging element and a similar disengaging element, said elements being disposed in substantially mutually parallel relationship; an electrical contact on each of said elements; said elements being similarly oriented so as to move simultaneously in the same direction when both are subjected to equal decreases of temperature and to move simultaneously in the opposite direction when both are subjected to equal increases in temperature; the electrical engaging element being adapted to move toward the electrical disengaging element when the former is subjected to a higher temperature than the latter, and the latter being adapted to disengage itself from the former when the latter is subjected to a higher temperature than the former; means to concentrate the rays of the sun on the electrical engaging element when the sun is in one position so as to cause the two contacts to engage each other and to concentrate the suns rays on the other element when the sun is in another position so as to cause disengagement of said contacts.

.perature of both elements 11. A heat responsive switch comprisingl `a base; an insulating strip secured thereto: two similarly oriented' bimetallic elements secured to the insulating strip at one end and spaced from the base at the other; a contact `secured to one of 'said elements; a second contact normally spaced from said rst contact 'secured to the free end of the second element so that when both of said elements are subjected to the same temperature, the contacts will be .spaced from each other, the vfree ends of the two elements moving simultaneouslyin one direction with increases in temand simultaneously in the opposite direction with decreases in temperature of both elements, one element moving so as to cause engagement between the two contacts when said element alone is subjected to a higher temperature than the second element and the second element moving so as to cause disengagement of the contacts when said element alone is subjected to an increase in temperature.

12. 'I'he combination set forth in claim 11, wherein there are means to subject the bimetallic elements individually to increased tempera.- tures.

13. A solar operated time signal device comprising an elongated hollow casing; a ray converging lens means at one end thereof; a heat responsive electrical switch at the other end thereof; a plurality. of spaced baffles positioned across said casing and intermediate said lens means and switch, said baffles, starting with the baille nearest the lens means, having elongated Aorifices of progressively smaller size, said elon JAMES M. BRADY. 

